The Extra Pharmacopoeia, originally produced by William Martindale in 1883 and now published by the Pharmaceutical Society of Great Britain, contains information on the drugs presently used in Great Britain. This edition has been entirely revised, reset, and increased in size because of the addition both of new drugs and of new material on drugs already described in previous editions. Although this edition appears only six years after the 23rd edition, it was necessary to increase the size by almost 350 pages. The general section contains about 1,400 pages of drug descriptions listed in alphabetical order under English titles. It was found to be convenient, however, to group certain classes of drugs such as the sulfonamides, the barbiturates, and a few others. Included under the specific drugs are a dosage statement, a brief physical description of the compound including solubilities, toxic effects, and incompatibilities, antidotes, contraindications, uses, sizes available, and